Mercedes-Benz F-Cell roadshow hits continent number three
April 7, 2011
Having crossed Europe and North America, the Mercedes-Benz F-Cell roadshow is now in Australia where the green-painted B-Class F-CELL cars are making the long trek from Sydney to Perth. Surrounding the small fleet is an entourage of more than a dozen vehicles including SUVs, Sprinter vans set up as mobile workshops and refuel stations and a semi-trailer laden with striking red full-length cylinders of hydrogen.
Benz wants the F-Cell World Drive, a four month global circumnavigation taking 14 countries, four continents and a wide gamut of climatic and driving conditions, to prove several points. In preparation for its introduction of fuel cell powertrains into its mainstream fleet in 2015, it wants to give buyers and legislators plenty of time to get used to what is to most a mysterious new technology. It wants to show its maturity and its readiness for everyday commuter use, and it wants to demonstrate its advantages over other electric drivetrains: long range, short refuel times, potential cost-effectiveness and zero emissions. All that and they've given it the feel (if not the sound) of a conventional internal combustion engined car.
The F Cell uses the fuel cell not as a direct source of power for the engine but as an on-board charger for its lithium-ion battery – as a range extender, similar to the way GM's Volt uses its petrol engine.
Fuel cell-charged EVs offer a couple of major advantages over their grid-charged counterparts in the form of longer range and shorter refuel times. They also have a couple of downsides. Firstly, they're less energy efficient, with the car having to carry a two-phase energy conversion system to stay mobile.
Then there's the matter of fueling infrastructure, of which there's virtually none at the moment. Benz is already running experimental fleets of F Cells on the roads in Europe and the US. Germany has all of 30 hydrogen fueling stations, of which only seven are public-access. The US has limited numbers – very limited numbers – in New York, Los Angeles and Michigan.
The primary advantage a hydrogen-sourced top-up offers over a conventional PHEV like the Volt presents at the exhaust outlet. It gives off nothing but steam. Measured well-to-wheels, Daimler and Linde – the global industrial gases giant providing mobile refueling facilities for the World Drive fleet – estimate hydrogen power in this form generates a greenhouse gas footprint about 30 per cent smaller than diesel. The only carbon emissions lie in the primary energy source used in extracting the hydrogen. Find a clean, renewable way to extract it – there are solar technologies showing some promise here – and it's near zero emissions, well to wheels.
Fuel consumption is measured in kilograms of hydrogen per 100 kilometers. Benz claims the F Cell uses less than 1kg/100km. That equates with about 3.3L/100km of diesel. Driven with due – but not obsessive – care, the company says a 4kg tank of hydrogen is good for a range of about 400km in urban environments, where the car is able to make best use of it energy regeneration systems during deceleration and braking.
Over the course of that 4kg tankful, the fuel cell will give off enough water vapor to condense into about 36 liters of water (which leaves one wondering if a world full of fuel cell vehicles might not live in something akin to a permanent La Nina event).
Fill costs? At the moment it costs 8-9 euros to fill a 4kg tank. With the rising economies of scale inevitable with the F Cell's mainstream release in 2015, the company's advice is that will drop to $2-3.
How a Fuel Cell Works
The principle of the fuel cell is generally described as being the reverse of water electrolysis. Essentially a controlled electrochemical reaction between hydrogen and oxygen in the air, it uses takes place within a simple cell comprising two electrodes (a cathode and an anode) separated by an electrolyte.
The process begins when hydrogen is fed into the anode side of the fuel cell, where each molecule is separated in the presence of the catalyst into an electron and a hydrogen ion.
The negatively charged electrons migrate to the cathode through the electric circuit, reacting with the oxygen.
While the positively charged protons migrate toward the cathode through a separating membrane, the electrons can't. They instead have to take the long, external way through the cathode. This transfer of electrons is expressed as electrical energy, which the unit directs into the Li-ion battery, keeping it charged.
Since the only by-products beyond that charge are water and heat, the unit produces no local pollution.
Read our full report on how the F-Cell drives.
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